Dartboard Scheme for Rate Enhancement of Mobile Free-Space Optical Channels

Free Space Optical (FSO) communication is one of the rising technologies due to its high data rates, secure nature, low cost and ease of deployment. Adding mobility to FSO technology enables its use in various applications, for example in ground-to-UAV and UAV-to-UAV communication. However, mobile FSO links suffer from increased link impairments due to misalignment and pointing errors. In this paper a new scheme for ground-to-UAV communication is proposed that compromises between beam availability and beam spreading. The new scheme, referred to as the dartboard scheme, uses two concentric laser beams with superposition modulation to enhance the average data rate of the link. Moreover, 4-PAM is also compared to the conventional use of OOK over mobile FSO links. Our simulations show that the dartboard scheme provides higher data rates than other schemes for a wide range of medium to low transmit powers. For example, at transmit power of 10 dBm, the dartboard scheme provides 53% higher data rate than 4-PAM, and 79% higher than OOK.